<!doctype HTML>
<div id="target1" style="width: 100px; height: 100px; background: blue;
                        -webkit-mask-image: linear-gradient(transparent, green)"></div>
<div id="target2" style="width: 100px; height: 100px; background: green;
                        -webkit-mask-image: linear-gradient(transparent, green)"></div>
<div id="target3" style="width: 100px; height: 100px; background: cyan"></div>
